1. Field of the Invention
The invention relates to an intake amount control apparatus of an internal combustion engine in which a fuel cut control is executed at the time of engine deceleration.
2. Description of the Related Art
In internal combustion engines, the amount of intake is adjusted through the adjustment of the opening amount of a throttle valve provided in an intake passageway, and the amount of fuel corresponding to the amount of intake is injected into an engine combustion chamber. This technology is disclosed in, for example, Japanese Patent Application Laid-Open Publication No. JP-A-08-074639. Furthermore, at the time of engine deceleration, a so-called termed fuel cut control that temporarily stops the injecting supply of fuel, provided that a predetermined condition is met, for example, the engine rotation speed is a predetermined rotation speed or higher, or the like, is performed so as to improve the fuel economy.
It is to be noted herein that although the fuel economy can be improved by executing the fuel cut control, the execution of this control causes no more combustion of fuel and naturally results in reduction in engine torque. Therefore, if the engine torque prior to the execution of the fuel cut control is large, the fuel cut control results in occurrence of a so-called torque shock. Hence, it can be said to be desirable to eliminate or reduce as much as possible the sudden change in engine torque associated with execution of the fuel cut control by reducing the engine torque as much as possible prior to the execution of the control.
An intake passageway downstream of the throttle valve, that is, an intake passageway extending from the throttle valve to the engine combustion chamber, is provided with members that have large capacities, for example, a surge tank, and the like. Therefore, even though the opening amount of the throttle valve is changed to a state near a completely closed state, that is, to an opening amount that allows maintenance of an idle operation, in accordance with deceleration of the internal combustion engine, the intake air remaining downstream of the throttle valve continues to be introduced into the engine combustion chamber after the changing. In particular, this tendency becomes very remarkable in an internal combustion engine equipped with a changing mechanism that changes the lift amount of the intake valves, since in this type of engine the lift amount is set at a reduced amount at the time of engine deceleration. Therefore, the engine torque can be reduced in expectation of execution of the fuel cut control, but only in a limited fashion. Furthermore, if the fuel cut control is executed after the engine torque has sufficiently reduced, the sharp change in engine torque can be eliminated or reduced, but the start of the fuel cut control is delayed, so that deteriorated fuel economy is inevitable.